Atherosclerotic cardiovascular disease remains a major cause of premature death and morbidity, in most regions of the world. Various transluminal, catheter-based interventional techniques have been used, or proposed for use, to dilate or otherwise treat atherosclerotic obstructions that occur in coronary and/or peripheral arteries. These therapies have traditionally focused on treating the disease intraluminally, or from “within” the vessel lumen.
Included among the newer interventional techniques are certain percutaneous, transluminal techniques for bypassing obstructions in coronary or peripheral arteries through the use of the adjacent vein(s) as in situ bypass conduit(s); (e.g. using catheters to perform extra luminal procedures outside the diseased vessel lumen. These procedures are described in U.S. Pat. No. 5,830,222 (Makower) and in published PCT Applications WO 98/16161 and WO 98/46119. As described therein, in some instances, these procedures may be performed by a venous approach wherein a tissue penetrating catheter is inserted into a vein and the desired passageway or puncture is initially formed by facilitating the passage of a tissue penetrator (e.g., a flow of energy or an elongate penetration member) from a catheter, through the wall of the vein in which the catheter is positioned, and into a target location such as the lumen of an adjacent vessel (e.g. the artery). Alternatively, some of these procedures may be performed by an arterial approach wherein the catheter is inserted into an artery and the desired passageway or puncture is initially formed by facilitating the passage of a tissue penetrator (e.g., a flow of energy or elongate penetration member) from the catheter, through the wall of the artery in which the catheter is positioned, and into the target location such as the lumen of an adjacent vessel (e.g. a vein). It is typically necessary for the tissue-penetrating catheter to be placed in proper rotational orientation within the blood vessel, prior to facilitating the passage of the tissue penetrator therefrom, to ensure that the tissue penetrator is aimed or positioned to enter the target. To facilitate such aiming of the tissue penetrator, some of the previously described tissue penetrating catheters have included a penetrator direction marker that indicates the direction in which the tissue penetrator will pass from the catheter and an imaging catheter lumen through which a separate intravascular ultrasound imaging catheter (IVUS catheter) can be advanced. After the separate IVUS catheter has been advanced into the imaging lumen of the tissue penetrating catheter, the IVUS is used to image the target and the penetrator direction marker. The catheter can then be rotated within the blood vessel until the penetrator direction marker is aligned with the target, thereby indicating that subsequent advancement of the tissue penetrator from the catheter will result in the formation of the desired penetration tract between the blood vessel in which the catheter is positioned and the target.
Applicant has determined that, in cases where the tissue-penetrating catheter is to be placed in a relatively small blood vessel such as branches of the coronary artery, carotid arteries, or smaller vessels located in the peripheral vasculature (e.g. vessels in the arms or legs), it is desirable for the tissue penetrating catheter to be of reduced profile while still having sufficient column strength and torque transfer properties to allow the operator to rotate and maneuver the distal end of the catheter within the patients body by twisting, pushing and pulling the proximal end of the catheter that remains outside of the patient's body. Thus, because the provision of a separate imaging catheter lumen substantially increases the required diameter of the tissue penetrating catheter, it is desirable to devise new tissue penetrating catheter designs that do not include an imaging catheter lumen while still maintaining the capability of imaging from a vantage point near the catheter's distal end to facilitate proper rotational orientation of the tissue penetrating catheter to facilitate aiming of the tissue penetrator.